Just FYI, my FWB JackHammer SCSI card freezes the computer if it is not properly terminated (with or without a device connected to the SCSI chain.)

I had to buy a ribbon SCSI terminator and terminate the ribbon cable on the internal 50 pin SCSI connector to get my computer to boot with it installed (but not connected to anything.)  So it might be worth checking your termination again, trying different active terminators just incase one you're using is broken.